Publications
of the
MPIfR
Optical & Infrared
Interferometry Group
T. Le Bertre, M. Matsuura, J.M.
Winters, H. Murakami, I. Yamamura,
M. Freund, and M. Tanaka:
Galactic mass-losing AGB stars probed with
the IRTS. I
Astronomy and Astrophysics 376, 997-1010 (2001)
Abstract.
AGB mass-losing sources are easy to identify and to characterize in
the near-infrared range (1-5 µm). We make use of the near-infrared
data acquired by the Japanese space experiment IRTS to study a sample
of sources detected in the 2 celestial strips surveyed by the
IRTS. Mass-loss rates and distances are estimated for 40 carbon-rich
sources and 86 oxygen-rich sources of which 8 are probably of
S-type. Although the sample is small, one sees a dependence of the
relative contribution of the two kinds of sources to the replenishment
of the interstellar medium (ISM) on the galactocentric
distance. E.g. from 6 to 8 kpc, oxygen-rich sources in our sample
contribute 10-12 times as much as carbon-rich sources, whereas from 10
to 12 kpc, the latters contribute 3-4 times as much as the
formers. Therefore, one would expect a gradient in the composition of
the ISM between 6 and 12 kpc from the Galactic Centre, especially in
its dust component. Most of the replenishment (> 50 %) by AGB stars
is
due to sources with mass-loss rate larger than
10-6Moyr-1.
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